1. Field of the Invention
The present invention relates to a termination (device), especially the one intended for high frequency applications.
2. Description of the Related Art
For example, U.S. Pat. No. 5,047,737 discloses an example of a conventional termination. FIG. 4 is a perspective view of the conventional termination, and FIG. 5 shows the cross-sectional view taken along the line 5—5 of FIG. 4. This termination 80 is comprised of a conductive piece 81 to electrically connect with the center conductor 81 of the other piece of the coaxial connector, a ground conductive piece 82 to electrically connect with an outer conductor of the other piece of the coaxial connector, and a resistive element 83 that is electrically connected between the conductor 81 and the ground conductive piece 82.
As described in the U.S. Pat. No. '737, in order to ground the coaxial impedance of the conductor 81 with the termination, the shape of the ground conductive piece needs to be carefully controlled. More specifically, the variance of the distance 85 in a cavity 84 between the resistive element 83 and the ground conductive piece 82 is important. In this case, in order to achieve generally constant resistance in any portion of the resistive element 83, the distance 85 between the resistive element 83 and the ground conductive piece 82 in the direction vertical to the axial direction of the resistive element 83 needs to be varied so as to form a suspended substrate line. However, it is difficult to form a smooth line.
As fully illustrated in FIG. 5, in the U.S. Patent, in order to solve the problem, in the cavity 84 between the resistive element 83 and the ground conductive piece, the ground conductive piece has a step-like surface and the surface is tapered down to the connecting section between the resistive element 83 and the ground conductive piece 82. However, with such step-like variance of the distance, it is impossible to provide a termination having stable performances especially for high frequency applications.
In addition, coaxial impedance that can be used (grounded) with a termination is usually determined by the ratio of outer diameter of a connecting section between the resistive element 83 and the conductor 81 to the outer diameter of the cavity around the connecting section. Especially in a high frequency termination, the former outer diameter has to be extremely small. However, the size of this outer diameter is easily affected by the height of the solder (not illustrated) applied for anchoring the resistive element to the conductor 81. Since it has been difficult to control the amount of the solder in the conventional termination, it has been difficult to achieve constant precision of the termination.
Furthermore, for example, the stress generated during the connection between termination and the connector significantly affects a relatively weak portion such as a soldered portion between the resistive element 83 and the conductor 81, and this stress has mechanically and electrically substantial impact on the termination. Therefore, there has been a demand of means to efficiently eliminate such stress.